The present invention relates, in general, to the art of earth boring and more particularly to a rotary rock bit constructed from at least one rock bit arm and a separate bearing journal or bearing pin. A rotary rock bit, in general, consists of at least one rock bit arm adapted to be connected to a rotary drill string. A cutter means in the form of a rotary cutter is mounted on a bearing pin extending from the rock bit arm. The cutter contacts the formations during the drilling operation to form the desired borehole. The present invention provides a rotary rock bit that is constructed from an individual rock bit arm and a separate bearing pin. The rock bit arm and bearing pin are joined together using a beam of energy.
The cutter is rotatably mounted on the bearing pin and a seal unit may be positioned between the cutter and the bearing pin or rock bit arm. The seal unit should function to provide a seal between the rock bit arm and the cutter to maintain lubricant within the bearing area and prevent fluids in the borehole from entering the bearing area. The seal should run against a smooth surface in order to maintain the integrity of the seal. The cutter movement during drilling is complex and includes rapid axial and radial as well as wobbling motions. The complex cutter movement increases the difficulty in providing a satisfactory seal.
The general concept of providing a bearing pin separate from the journal was previously known; however, the novel means of joining the bearing pin to the rock bit arm was not known prior to applicant's present invention. The present invention provides an improved rotary rock bit by allowing the joining of optimum bearing steel to optimum rock bit arm steel. The problems and expense of manufacturing are reduced by allowing the rock bit arm to be constructed of an appropriate grade of steel. The bearing pin can be machined separate and apart from the rock bit arm. The metallurgical processing is simplified because the bearing pin can be treated separate from the rock bit arm. The bearing pin material need not be compatible with the arm material for heat treating process. Various bearing angles and offsets are provided.